Interplay between base-salt relief, progradational sediment loading and salt tectonics in the Nordkapp Basin, Barents Sea - Part II

Reprocessed, regional, 2D seismic reflection profiles, 3D seismic volumes and well data (exploration and shallow boreholes), combined with 2D structural restorations and 1D backstripping were used to study the post-salt evolution of the Nordkapp Basin in Barents Sea. The post-salt evolution took place above a pre-salt basement and basin configuration affected by multiple rift events that influenced the depositional facies and thickness of Pennsylvanian-lower Permian-layered evaporite sequence. Initially, regional mid-late Permian extension reactivated pre-salt Carboniferous faults, caused minor normal faulting in the Permian strata and triggered slight salt mobilization towards structural highs. The main phase of salt mobilization occurred during earliest Triassic when thick and rapidly prograding sediments entered from the east into the Nordkapp Basin. In the early-mid-Triassic, the change in the direction of progradation and sediment entry-points shifted to the NW led to rotation of the earlier-formed mini-basins and shift of dominant salt evacuation direction to the south. The prograding sediment influx direction, sediment transport velocity and thickness influenced the dynamics of the early to late passive diapirism, salt expulsion and depletion along the strike of the basin. The basin topography resulting from salt highs and mini-basin lows strongly affected the Triassic progradational fairways and determined the distinct sediment routing patterns. Minor rejuvenation of the salt structures and rotation of the mini-basins took place at the Triassic-Jurassic transition, due to far-field stresses caused by the evolving Novaya Zemlya fold-and-thrust belt to the east. This rejuvenation influenced the sediment dispersal routings and caused formation of dwarf secondary mini-basins. The second and main rejuvenation phase took place during likely early-mid-Eocene when propagated far-field stresses from the transpressional Eurekan/Spitsbergen orogeny to the NW inverted pre-salt normal faults, reactivated the structural highs and rejuvenated the salt structures. The studied processes and study outcomes can be applicable to other evaporite-dominated basins worldwide.

Automated summary

Reprocessed seismic data and well information were used to study the post-salt evolution of the Nordkapp Basin, revealing the influence of multiple rift events on pre-salt rocks and the dynamics of salt mobilization and structural rejuvenation in different geological periods.